The development of bioimpedance anlysis (BIA) is a major advance in body composition analysis. Early systems were almost entirely 50 kHz, but new BIA systems can scan from very low to high frequencies. These "multifrequency" BIA systems (MFBIA) collect large amounts of electrical data, and when compared to several 'gold standard' measurements, e.g., water dilution techniques and DXA, the impedance data can be modeled to obtain clinical estimates of compartmental volumes and mass. Tanita Corporation (Arlington Heights, IL) has developed a new MFBIA system. The present study is designed to examine two specific aims using the newly developed instrument and compare its measurements with other systems available in the market. Aim 1: To determine the variation in impedance measurements by altering the position of electrode placements on the body. The goal is to develop accurate, reproducible, and practical measurement protocols. Aim 2: To develop multiple frequency prediction models for total body water, extracellular water, body cell mass, fat-free body mass, skeletal muscle, and fat: and to determine the validity of these models by cross-validation in a second study cohort to include special populations such as patients and body builders. The goal is to develop and validate generalizable prediction formulas that can be applied in subjects who are both healthy, and who have acute/chronic diseases.